“We’re so fortunate to have this amazing landmark in our community,” said Gigi Gleason, chair of the capital campaign committee raising money for the work. “I really believe it’s not only our responsibility but our privilege to preserve this landmark not only for our generation, but generations to come.”

The first step of that preservation for the Mission San Luis Rey is to remove the roof of the church, bore holes in the walls and reinforce parts of the building with rebar, giving the adobe structure some room to wriggle. More important, said Executive Director and Franciscan friar David Gaa, is to reinforce the roof with steel to make it one solid piece so it won’t come crumbling down in serious rumbling.

The adobe church building was completed in 1815, years after the mission was founded in 1798. Much of the artwork, a piano and an organ have been removed because the construction will create dust that could be harmful. It has been more than a century since the artwork was removed from the church, Gaa said.

One of the most recognizable works, however, remains in the church. At the front of the sanctuary a crucifix, which, according to Gaa, is older than the church itself, is shrouded in bedsheets. It was too fragile to placed in storage, he said.

The work is expected to cost $3.1 million. About $640,000 of that is from the National Park Service grant program Saving America’s Treasures.

“My hope is when people see the scaffolding and the work that’s being done, that we will be able to raise the rest of the funds,” Gaa said. “If not, I don’t have a backup plan.”

Gleason said she is confident the remaining funds will come through.

“The worst-case scenario is that we would have to close the church to the public, and that’s not an option,” Gleason said.

More than $3 million has been raised so far in either cash donations, pledges or commitments, with about $94,000 remaining to be raised. The federal grant is contingent upon the work being completed by the end of the year, and will not be disbursed until the project is complete and the National Park Service approves the work.

Ultimately, the retrofits are necessary if the Mission’s church is to stay open to the public. The landmark is owned by the Franciscan Friars, headquartered in Oakland. Typically, much of the Mission San Luis Rey grounds are closed to the public but are used and tended to by the monks.

The celebration Saturday will allow patrons to explore parts of the campus that are often off-limits.

“The idea is to throw the whole place open,” Gaa said. “One of the things we friars believe very much is that even though the mission is owned by the Franciscan Friars, the mission belongs to the people.”

The private inner gardens will be opened today. There will also be a ladybug release at 10 a.m. in the rose gardens and live entertainment. The insects help the gardens thrive naturally.

Visitors can buy a barbecue lunch and receive a 10 percent discount in the gift shop. Native plants, succulents and annuals from the mission will be sold from 10 a.m. to 3 p.m.

The mission is at 4050 Mission Ave.

The church is still open for tours during construction Fridays, Saturdays and Sundays, when work is paused.